Programmable acoustic sensors are a class of MEMS devices that includes microphones. Conventional programmable acoustic sensors typically can include for example a MEMS transducer that is in contact with acoustic pressure. Acoustic pressure variations may cause one or more electrical parameters of the MEMS transducer to change. The MEMS transducer can be formed from for example but not limited to, a diaphragm or a suspended plate. Increasing acoustic pressure causes a diaphragm to bend or a translational displacement of a suspended plate.
A programmable acoustic sensor is utilized to sense a change in the electrical parameters of the MEMS transducer and produces an electrical output signal that is a measure of the acoustic pressure. The electrical parameters sensed by the programmable acoustic sensor can be of many forms, including but not limited to, a capacitance change determined by a bending of a diaphragm or displacement of a suspended plate.
A response of the MEMS transducer to an acoustic pressure change is typically a function of the mechanical parameters of the MEMS transducer. The programmable acoustic sensor also has its own variations, which in general are substantially smaller than the mechanical ones of the MEMS transducer. Therefore, an input signal provided from the MEMS transducer to the programmable acoustic sensor that varies widely in voltage can result in sub-optimal performance of the acoustic sensor. Hence to minimize yield loss in manufacturing due to large variations in the mechanical parameters of the MEMS transducer, it is desirable that the acoustic sensor be programmable.
Programmability can also be used to enhance testability and observability of the programmable acoustic device, which can further improve the test accuracy and reduce the test cost. Programmability may be used to compensate for variations in key sensor parameters, for example but not limited to, transducer sensitivity, signal to noise ratio (SNR), resonance frequency of the mechanical element of the transducer, and a phase delay of the acoustic sensor.
What is needed whether in a digital or analog sensor is a system and method for increasing the functionality of the sensor without increasing the number of pins utilized on the sensors. The system and method should be simple, cost effective and adaptable to existing environments. The present invention addresses such a need.